linux-kernel - [PATCH 3/8] tty: n_gsm: Modify CR,PF bit when config requester

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Message-Id: <1629461872-26965-3-git-send-email-zhenguo6858@gmail.com>
Date:   Fri, 20 Aug 2021 20:17:47 +0800
From:   Zhenguo Zhao <zhenguo6858@...il.com>
To:     nianfu.bai@...soc.com, gregkh@...uxfoundation.org,
        jirislaby@...nel.org
Cc:     linux-kernel@...r.kernel.org
Subject: [PATCH 3/8] tty: n_gsm: Modify CR,PF bit when config requester

From: Zhenguo Zhao <Zhenguo.Zhao1@...soc.com>

When n_gsm config "initiator=0",as requester,gsmld receives dlci SABM/DISC
control command frame,but send UA frame is error.

Example:
Gsmld receive dlc0 SABM frame "f9 03 3f 01 1c f9",now it sends UA
frame "f9 01 63 01 a3 f9",CR and PF bit are 0,but it should be set
1 from requster to initiator.

Kernel test log as follows:

Before modify

[  271.732031] c1 gsmld_receive: 00000000: f9 03 3f 01 1c f9
[  271.741719] c1 <-- 0) C: SABM(P)
[  271.749483] c1 gsmld_output: 00000000: f9 01 63 01 a3 f9
[  271.758337] c1 --> 0) R: UA(F)

After modify

[  261.233188] c0 gsmld_receive: 00000000: f9 03 3f 01 1c f9
[  261.242767] c0 <-- 0) C: SABM(P)
[  261.250497] c0 gsmld_output: 00000000: f9 03 73 01 d7 f9
[  261.259759] c0 --> 0) C: UA(P)

Signed-off-by: Zhenguo Zhao <Zhenguo.Zhao1@...soc.com>
---
 drivers/tty/n_gsm.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index becca2c..7aa10de 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -601,7 +601,7 @@ static void gsm_send(struct gsm_mux *gsm, int addr, int cr, int control)
 
 static inline void gsm_response(struct gsm_mux *gsm, int addr, int control)
 {
-	gsm_send(gsm, addr, 0, control);
+	gsm_send(gsm, addr, 1, control);
 }
 
 /**
@@ -1786,9 +1786,9 @@ static void gsm_queue(struct gsm_mux *gsm)
 		if (dlci == NULL)
 			return;
 		if (dlci->dead)
-			gsm_response(gsm, address, DM);
+			gsm_response(gsm, address, DM|PF);
 		else {
-			gsm_response(gsm, address, UA);
+			gsm_response(gsm, address, UA|PF);
 			gsm_dlci_open(dlci);
 		}
 		break;
@@ -1796,11 +1796,11 @@ static void gsm_queue(struct gsm_mux *gsm)
 		if (cr == 1)
 			goto invalid;
 		if (dlci == NULL || dlci->state == DLCI_CLOSED) {
-			gsm_response(gsm, address, DM);
+			gsm_response(gsm, address, DM|PF);
 			return;
 		}
 		/* Real close complete */
-		gsm_response(gsm, address, UA);
+		gsm_response(gsm, address, UA|PF);
 		gsm_dlci_close(dlci);
 		break;
 	case UA:
-- 
1.9.1